Pedigrees

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Pedigrees
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Pedigrees

• A type of chart that is used to show the patterns
  of transmission of a trait within a given family
• Usually produced after an undesirable trait
  appears within a family
• Used to figure out the ways that the trait might
  be passed along, to counsel parents on the cause
  of the disease or in predicting the probability
  of parents having an affected child

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Pedigree Patterns affected by

• Whether it is an autosome or X-linked gene
• Whether the trait is dominant or recessive
• The chance of transmission of the gene from the
  parents to the children
• Can be confusing if multifactorial traits are
  involved

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Here is a list of symbols that are commonly used
when making pedigrees
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Autosomal Recessive Inheritance

• Both parents of an affected individual must be
  heterozygous
• Affected individuals might skip generations
• Males and females are affected in equally.

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Autosomal Dominant Inheritance

• Half the children of an affected parent are
  generally affected.
• The trait is transmitted only by affected
  individuals and does not skip generations
• Males and females affected equally.
• Father to son transmission is possible

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X-linked Recessive Inheritance

• No father to son transmissions
• Father to daughter carrier is possible
• Female carrier will transmit to half her sons
• Males are affected the most.
• Skips generations

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Questions

• Page 198 Read through sample problems 1 and 2.
• Page 199 Practice problem 1 and 2
• Page 201 1-5